JPS631369B2 - - Google Patents
Info
- Publication number
- JPS631369B2 JPS631369B2 JP58138724A JP13872483A JPS631369B2 JP S631369 B2 JPS631369 B2 JP S631369B2 JP 58138724 A JP58138724 A JP 58138724A JP 13872483 A JP13872483 A JP 13872483A JP S631369 B2 JPS631369 B2 JP S631369B2
- Authority
- JP
- Japan
- Prior art keywords
- less
- hic
- steel
- rolling
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910000831 Steel Inorganic materials 0.000 claims description 56
- 239000010959 steel Substances 0.000 claims description 56
- 238000001816 cooling Methods 0.000 claims description 31
- 238000005096 rolling process Methods 0.000 claims description 25
- 230000007797 corrosion Effects 0.000 claims description 18
- 238000005260 corrosion Methods 0.000 claims description 18
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 12
- 229910052739 hydrogen Inorganic materials 0.000 claims description 12
- 239000001257 hydrogen Substances 0.000 claims description 12
- 238000005336 cracking Methods 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 229910052791 calcium Inorganic materials 0.000 claims description 8
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims description 5
- 230000009467 reduction Effects 0.000 claims description 5
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 229910052717 sulfur Inorganic materials 0.000 claims description 4
- 230000009466 transformation Effects 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 claims 1
- 238000000034 method Methods 0.000 description 18
- 230000000694 effects Effects 0.000 description 16
- 229910001563 bainite Inorganic materials 0.000 description 12
- 238000010438 heat treatment Methods 0.000 description 12
- 238000005204 segregation Methods 0.000 description 12
- 239000000463 material Substances 0.000 description 11
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 6
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 6
- 229910001566 austenite Inorganic materials 0.000 description 6
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000003466 welding Methods 0.000 description 5
- YZCKVEUIGOORGS-UHFFFAOYSA-N Hydrogen atom Chemical compound [H] YZCKVEUIGOORGS-UHFFFAOYSA-N 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000010953 base metal Substances 0.000 description 4
- 230000006866 deterioration Effects 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 3
- 239000001569 carbon dioxide Substances 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000035882 stress Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 238000003303 reheating Methods 0.000 description 2
- 229910000532 Deoxidized steel Inorganic materials 0.000 description 1
- 229910000655 Killed steel Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 239000010779 crude oil Substances 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000006355 external stress Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000029052 metamorphosis Effects 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000013001 point bending Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000012047 saturated solution Substances 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000011265 semifinished product Substances 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Description
〔産業上の利用分野〕
本発明は鋼の成分に特別な条件を設けるととも
に加熱圧延条件及び圧延直後の冷却条件を制御す
ることにより、湿潤な硫化水素環境（以後サワー
環境と言う）、とくに高濃度の硫化水素あるいは
さらに二酸化炭素を含む湿潤環境下において耐水
素誘起割れ性及び耐硫化物応力腐食割れ性の優れ
た鋼板の製造方法に関するものである。
〔従来技術〕
近年、パイプラインの敷設が大規模的に行なわ
れているが、このようなパイプラインにおいて腐
食による材料の劣化が問題となつている。特に石
油や天然ガスのパイプライン輪送において原油や
天然ガスに硫化水素（以後H2Sと言う）や二酸化
炭素（以後CO2と言う）を含む場合が多く、これ
らのH2S、CO2は水と共存し腐食作用により発生
した原子状の水素が鋼中に侵入して起る破壊が問
題となつている。
この腐食作用により発生した原子状の水素が鋼
中に浸入して起る破壊には、板面に平行な割れで
ある水素誘起割れ（以後HIC）と板面に垂直な割
れである硫化物応力腐食割れ（以後SSC）とがあ
る。
HICの発生機構は、サワー環境下で起こる鋼材
表面の鉄の腐食によつて生じた原子状の水素が鋼
中に侵入し、鋼材中のMnSや酸化物系のクラス
ターのような層状の広がりをもつ介存物のまわり
に集積して起るものである。しかもかかる層状の
介在物はしばしば偏析帯の中に存在するために、
介在物を起点に発生したHICが偏析帯によつて助
長されることが知られている。
一方、SSCは特に高強度側で起る現象であり、
更に、ラインパイプ等の製造、敷設に際しては溶
接施工が必須となるから、これらの用途に供され
る鋼の溶接部の硬度は高くなり、パイプラインの
操業化及び残留応力と鋼中の原子状の水素により
SSCが発生することが知られている。
しかして従来これらのHIC、SSCの防止には以
下の様な手段が用いられている。
HICについては、(1)Ni、Cu、Cr等のように鋼
の腐食を抑制するか、あるいは表面に安定皮膜を
形成する元素を添加して腐食にともなう侵入水素
を低減させる方法、(2)Ca、REM等を添加しMnS
を球状化させる方法、(3)Mn、Ｐ等の含有量を低
減し、あるいは圧延半成品を均熱拡散処理するこ
とによつて偏析帯の偏析度を低下させる方法、(4)
圧延後、再加熱を行ない焼入れ焼戻し、又は焼な
らしを施することによつて主として偏析部のミク
ロ組織を改善することによつてHIC感受性を低く
する方法、などが試みられてきた。
一方、SSCの防止手段としては、(i)鋼板の表面
硬度をさげる、(ii)施工時の溶接条件を制限する、
等の対策が行なわれてきた。
しかしながら腐食環境条件がこれまでのところ
で最も厳しいとされているPH3.0のH2S人工海
水飽和溶液ではHIC及びSSCを完全に防止するこ
とが出来なかつた。それは以下の様な問題点を有
していたからである。
HICについての問題点は以下のとおりである。
〔発明の目的〕
前記(1)の方法により鋼にCu添加ないしはNi、
Cr添加をすることによつて鋼の腐食を抑制し、
それによつて鋼中への水素侵入を抑制しようとす
る場合には、PHの下限制約が存在し、例えばCu
はPH５以上であれば安定な腐食生成物を生成する
が低PHになるとCuの腐食生成物は溶解し、水素
侵入を抑制することが出来ない。また通常パイプ
ラインではパイプ内の堆積物を除去するために定
期的にピグ（Pig）と称する内部清掃用の器具を
導通させる。このPigの擦過によつて生じる傷の
ために局部的な腐食は避け得ない。
前記(2)の方法ではHICの発生点であるMnSを
球状化するためにCa、REM等の添加を行なつて
いるが、鋼片の中心部は不純物が多く集積するた
め完全にMnSを球状化することはむずかしい。
また、中心部を完全に球状化しようとすれば多量
のCa、REMの添加が必要となり中心部以外では
クラスター状の酸化物系介在物が増加しHICの原
因となる。したがつてHICの発生点であるMnS
を完全に球状化することはむずかしい。
(3)の方法に関して言えばＰ、Mn等の偏析を助
長しやすい元素をできるかぎり低めてHICの伝播
を防止しようとするものであるが、この方法は次
の２点でHICを完壁に抑制しようとすると不十分
である。すなわち第１に伝播経路を取り除いても
発生点を除去しないことにはHICはなくならな
い。第２に今日の工業技術からみて大量生産には
適用できないような制限範囲、たとえば鋼中のＰ
を0.002％以下と極端に下げる条件を設けなけれ
ばならず実用上採用できないなどが指摘できよ
う。
前記(4)の方法、すなわち圧延後、再加熱を行な
い、焼入れ焼戻し、又は焼ならしを施こす方法は
(3)の方法と基本的には考え方を一にするものであ
るが(3)の方法が大量製造工程には採用できないの
にくらべて現実的には有用な手段である。しかし
ながら、(3)の方法と同様HICの発生点を除去しな
いかぎりは完全なHICフリー鋼とはならない。た
だしQT処理材は同一介在物形態制御の圧延まま
材と比較してHIC感受性が改善される。
一方SSCの問題としては、次のとおりである。
(i)HICの(4)で述べたQT処理はHICの割れ感受
性を改善させるが、加熱後直接水冷するため焼戻
処理を行なつても表面硬度が板厚中心部と比較し
て非常に高い。したがつてサワー環境下ではHIC
に有利であるが、SSCが発生しやすく、問題とな
る。
前記した(ii)の施工時の溶接条件の制限は、溶接
入熱が低いと熱影響部（HAZ）に焼きが入り硬
化組織が生成され硬度を高めSSCを発生するた
め、その対策として、例えば溶接入熱を上げ硬度
を低下させるものであるがHAZ部の靭性を劣下
させる等の問題がある。
以上の事から高濃度の硫化水素あるいは二酸化
炭素を含む湿潤環境下においてHIC及びSSCを完
全に防止することは出来なかつた。
〔発明の構成〕
本発明者らは上記の欠点を解決すべく成分系、
加熱、圧延、冷却プロセスについて鋭意研究の結
果、鋼板の強度、靭性は勿論であるが、耐HIC、
耐SSC特性の優れた全く新しい鋼板の製造法を発
明するに至つた。
以下この点について詳しく説明する。
本発明の特徴は、Ｓ含有量を極端に下げるとと
もにCa添加によりMnSの形態制御処理を実施し、
Mo、Ti添加した鋼片を加熱し、オーステナイト
粒の再結晶域の圧延に加えて、900℃以下の未再
結晶域で60〜80％の圧下を加え、Ar3変態点以上
で圧延を終了した後、直ちに比較的速い冷却速度
20超〜40℃／secで冷却し350℃以上550℃未満の
温度で水冷停止し、その後放冷することにある。
この方法に従えば冷却後の組織は微細なベイナ
イトあるいは微細なフエライト−ベイナイトの混
合組織となり板厚方向の硬度は一定となり、また
中心偏析部のミクロ組織も改善され、強度、靭性
は優れ、耐HIC耐SSC性も非常に改善される。
又、耐ラメラ−テア性、耐溶接熱影響割れ性の改
善も大である。
このため本発明鋼はあらゆる用途（化学プラン
ト機器、圧力容器、造船、ラインパイプ等）に適
用可能である。
〔発明の作用効果〕
以下本発明における加熱、圧延、冷却条件の限
定理由について詳細に説明する。
まず、加熱温度を1000〜1200℃に限定した理由
は、加熱時のオーステナイト粒を小さく保ち、圧
延組織の細粒化をはかるためである。1200℃は加
熱時のオーステナイト粒が粗大化しない上限温度
であつて、加熱温度がこれを超えるとオーステナ
イト粒が粗大化し、冷却後のフエライト、ベイナ
イト組織も粗大化するため鋼の靭性が劣化する。
一方、加熱温度が余りに低すぎると、添加合金
元素が十分に溶体化されず、鋼の内質が劣化する
と共に、圧延終段の温度が下がり過ぎるため、制
御冷却による十分な材質向上効果が期待できな
い。このため下限を1000℃とする必要がある。
しかしながら、加熱温度を上記のように制限し
ても圧延条件が不適当であると良好な材質を得る
ことができないため、900℃以下の未再結晶温度
域での圧下量が60％以上必要である。これは低温
加熱に未再結晶温度域での十分な圧延を加えるこ
とによつて細粒オーステナイトの延伸化を徹底
し、冷却後に生成する変態組織を細粒均一化する
ためであり圧下量が60％未満であるとその効果は
小さい。また上限を80％としたのは80％を超える
と圧下のパス回数が増加し仕上温度が確保されな
いため80％とした
このように細粒オーステナイトを十分延伸化す
ることにより、圧延冷却後生成するフエライト−
ベイナイト組織を十分細粒化しないと、靭性が大
巾に劣化するばかりでなく、板厚方向の硬度差が
大きくなり、耐SSC性も劣化する。
圧延仕上げ温度は特殊な組織を発達させないと
共に、HICに影響を与えるMnSの伸長化を防止
し、又次工程の水冷効果を発揮させるため、Ar3
変態点以上とする。
次に圧延後の冷却であるが、これは良好な強
度、靭性及び耐HIC、耐SSC性を得るために板厚
方向に均一なフエライト−ベイナイト組織が得ら
れるように行なわなければならない。
冷却開始温度は、均一で微細なフエライト−ベ
イナイト組織を得るためにAr3変態点以上が好ま
しい。ただしAr3−30℃までは有効である。しか
しそれ以下になるとミクロン組織中の粗大フエラ
イト量が多くなり耐HIC特性に必ずしも有効でな
くなる。
冷却及び冷却停止温度条件の限定は本発明の耐
HIC、耐SSC性改善のための必須条件であり、以
下その理由について述べる。
冷却は、圧延終了直後から350℃以上550℃未満
の温度まで20℃超〜40℃／secの範囲の冷却速度
で実施する必要がある。この理由は20℃／sec未
満では微細なフエライト−ベイナイト組織が生成
しにくく、40℃／sec超では多量のマルテンサイ
トが生成し耐HIC特性を劣化させるばかりでな
く、靭性をも劣化させる。したがつて耐HIC特性
の改善には組織を均一、且つ微細なフエライト−
ベイナイトに制御することが必須条件である。又
冷却停止温度については、均一で且つ微細なフエ
ライト−ベイナイトを得るために下限を350℃で
上限を550℃未満とした。
第１図に本発明鋼の水冷停止温度とHIC−
UST欠陥面積率（％）との関係を示す。
第１図に示す如く、水冷停止温度が550℃未満
では微細なフエライト−ベイナイト組織となり、
中心偏析部の組織も改善され、その効果により耐
HIC特性も向上する。
水冷停止温度550゜以上では組織としてはパーラ
イトが一部分ベイナイト化するが、層状組織が残
留しHIC特性はある程度改善されるが十分ではな
い。また下限の350℃未満であると硬化組織が生
成し、HIC特性及びSSC特性を劣化させる。
第２図に板厚方向の硬度分布を示したが、550
℃未満で水冷停止した鋼は板厚方向の硬度差が小
さく、通常QT材より同一強度レベルでの表面硬
度が非常に低くなり、その結果、耐SSC特性が著
しく改善され、高強度厚肉材が製造可能となる。
以下本発明鋼の成分範囲の限定理由について説
明する。
上記特徴を持つ本発明鋼中第１発明の鋼の成分
範囲はＣ：0.12％以下、Si：0.6％以下、Mn：0.6
〜1.5％、Ｐ：0.015％以下、Al：0.01〜0.10％、
Ti：0.005〜0.025％、Mo：0.1〜0.5％を基本成分
としてＳ、Ｏ、Caの含有量がＳ：0.003％以下、
Ｏ：0.005％以下、Ca：0.006％以下であつて、か
つ
0.7≦〔Ca〕／1.25〔Ｓ〕＋0.625〔Ｏ〕≦1.5
の条件を満足させたものである。
HICの原因は(1)非金属介在物、(2)腐食反応によ
る水素侵入、(3)偏析等に起因する内質の劣化によ
る。
まず最初に(1)の非金属介在物対策について述べ
る。本発明鋼において不純物であるＳを0.003％
以下、Ｏを0.005％以下、Caを0.006％以下に限定
し、更にこの３成分の関係が0.7≦
〔Ca〕／1.25〔Ｓ〕＋0.625〔Ｏ〕≦1.5の条件を満足す
るよう
に規定した主なる理由は、HICの発生主因である
MnSの球状化と主に低PH域でHICの起点となる
クラスター状の酸化物系介在物の減少にある。こ
の対策として鋼中のＳ量、即ち、MnS、の絶対
量を減少させ、更にCa添加によりMnSを形態制
御すると共にＯ量即ちAl2O3の絶対量を減少さ
せ、Ca添加によりクラスター状の酸化物である
Al2O3を還元させ球状のCaO・Al2O3に転化させ
る。このための条件を鋭意検討した結果、本発明
者は、Ｓを0.003％以下と少なくした上で、
〔Ca〕／1.25〔Ｓ〕＋0.625〔Ｏ〕を0.7以上にすること
によ
り、伸長介在物MnSを極端に減少させることが
可能である。同様に〔Ca〕／1.25〔Ｓ〕＋0.625〔Ｏ〕
を1.5以
下に抑えることによりクラスター状の酸化物系介
在物の発生量を最少に抑えることが可能であり、
耐HICに顕著な効果が認められることを見出し
た。このためＳの上限を0.003％とし、
〔Ca〕／1.25〔Ｓ〕＋0.625〔Ｏ〕の上限を1.5、下限を
0.7と
した。又Ｓは低い程改善効果が大きく、0.001％
以下にすることにより飛躍的に向上する。
次に(2)の腐食反応による水素侵入防止について
述べる。
Fe→Fe++＋2e-、2H+＋2e-→2Hの腐食反応に
より発生した原子状の水素が鋼中に侵入しHICの
原因となる。一般的な対策としてはCu等を添加
して安定な表面皮膜を生成させているが低PH域で
はその効果が薄れてくる。
したがつて、本発明者は低Hz域において水素が
鋼中に侵入してもHICを発生させない方法につい
て検討を行つた。(3)の内質の劣化については中心
偏析を軽減するMo添加と前述した加熱、圧延、
冷却条件の限定で組織の改善を行う。
次に各成分の限定理由について説明する。
Ｃの上限を0.12％としたのは母材及び溶接部の
強度確保のためであるが、0.12％を超えると制御
冷却した場合島状マルテンサイトが生成し、延靭
性に悪影響を及ぼすばかりでなく、内質、溶接性
及びHAZ靭性も劣化させるため上限を0.12％と
した。
なお、Ｃは0.03％未満であれば中心偏析部を非
常に改善することから0.03％未満が好ましい。
Siは脱酸上鋼に必然的に含まれる元素であある
が、Siもまた溶接性及びHAZ部靭性を劣化させ
るため上限を0.6％とした（鋼の脱酸はAlだけで
も可能であり好ましくは0.2％以下が望ましい）。
Mnは強度、靭性を同時に向上せしめる極めて
重要な元素である。Mnが0.6％未満では低Ｃであ
るため強度が確保できず、靭性改善効果も少ない
ため下限を0.6％とした。しかしMnが多過がて焼
入性が増加するとマルテンサイトが多量に生成し
易くなると共に、中心偏析が著しくなり、HIC伝
播停止能力が低下する。又、母材及びHAZの靭
性を劣化させるため、その上限を1.5％とした。
Ｐについては、中心偏析を助長する元素である
から上限を0.015％以下とした。
Alは脱酸上この種のキルド鋼に必然的に含有
される元素であるが、Al0.01％未満では脱酸が不
十分となり、母材靭性が劣化するため下限を0.01
％とした。一方Alが0.10％を超えるとクラスター
状の酸化物系介在物が増加し、HICに悪影響を及
ぼすと共に、HAZ靭性が劣化するため上限を
0.10％にした。
Tiは添加量が少ない範囲（Ti0.005〜0.025％）
では微細なTiNを形成し、圧延組織及びHAZの
細粒化、つまり靭性向上に効果的である。又Ti、
Caの相乗効果によりHICの発生原因であるMnS
を球状化する効果もある。したがつてTi添加量
の下限は材質上の効果が発揮される最少量であ
り、上限は微細なTiNが鋼片中に通常の製造法
で得られ、またTiCによる靭性劣化が起きない条
件から0.025％とした。
Moについては低PH環境においてHICに有効な
元素であるが0.1％以下ではこの効果は小さく、
又0.5以上ではこの効果が薄く、かつコストアツ
プになるため上限を0.5％とした。
Ｏ、Caについてはすでに詳しく説明したが、
Ｏの上限を0.005％としたのは0.005％を超えると
クラスター状の酸化物系介在物が増加しHICの原
因となるため上限を0.005％と制限した。Caにつ
いてはICPとの関係があるが、Ca量の上限を
0.006％と制限したのはＯと同様、0.006％を超え
るとクラスター状の酸化物系介在物が増加し、
HICの原因となるため上限を0.006％と制限した。
特許請求の範囲第２項に示した第２の発明にお
いては、第１項に示した第１の発明の鋼の成分及
び製造プロセスにさらにNb：0.10％以下、Ｖ：
0.10％以下、Ni：1.0％以下、Cu：1.0％以下、
Cr：1.25％以下、Ｂ：0.005％以下の１種又は２
種以上を含有させるものである。
これらの元素を含有させる主たる目的は本発明
鋼の特徴を損なうことなく、強度、靭性の向上及
び製造板厚の拡大を可能とすることにあり、その
添加量は自ら制限されるべき性質のものである。
Nbは圧延組織の細粒化、焼入性の向上と析出
硬化のため含有させるもので強度、靭性を共に向
上させる重要な元素であるが、制御冷却材では
0.10％を超えて添加しても材質上効果なく、また
溶接性及びHAZ靭性に有害であるため上限を
0.10％に限定した。
ＶはNbとほぼ同様の効果をもつが、上限はい
ずれも0.10％まで許容できる。
Niは耐食性、耐HIC特性等に効果的な元素で
あり、しかも母材の強度、靭性を向上させる。し
かし、１％を超えると耐SSC性及びHAZの硬化
性、靭性に好ましくないため上限を１％とした。
Cuは、前述の如く比較的PHの高いサワー環境
での水素侵入防止に有効であるが、１％を超える
とNiを添加しても圧延中にCu−クラツクが発生
し、製造が難しくなる。このため上限を0.1％と
した。
Crは母材及び溶接部の強度を高め、耐HIC性
等にも効果を有するが多きに失するとHAZの硬
化性を増大させ靭性及び溶接性の低下を招き好ま
しくない。その上限は1.25％である。
Ｂは圧延中にオーステナイト粒界に偏析し、焼
入性を上げベイナイト組織を生成しやすくする
が、0.005％超になるとBNやＢ constituentを
生成するようになるため母材及びHAZの靭性を
劣化させる。このため上限を0.005％とした。
〔実施例〕
次に本発明の実施例について説明する。
転炉一連鋳工程で製造した第１表の化学成分の
鋳片を用い、加熱、圧延、冷却プロセスを変えて
板厚12〜32mmの鋼板を製造した。
鋼１〜９は本発明鋼であり、又鋼１０〜１４は
比較鋼である。
第２表には機械的性質及び耐HIC特性、耐SSC
特性を示す。HIC試験は鋼板より表裏面１mm切削
した厚さで、巾20mm、長さ100mmの試験片を用い、
又SSC試験は厚さ３mm、巾10mm、長さ115mmの試
験片を用いて行なつた。
試験条件としてはHIC試験は外部応力を負荷せ
ずに行ない、SSC試験は４点曲げ治具により降伏
応力に相当するたわみを試験片に負荷した。浸漬
条件としては25℃のH2S飽和で0.5％CH3COOH
−５％NaCl水溶液（PH３）中に、HIC試験片
は４日間、SSC試験片は21日間浸漬した。浸漬結
果を第２表に示す。
比較鋼中、鋼１０はICPが0.30と低いためその
他の条件は適正な製造条件の範囲であるにもかか
わらずHICが発生する。
鋼１１は鋼１０とは逆でICPが1.66と高いため
HICが発生する。
鋼１０，１１は本発明鋼３〜５と同一の化学成
分であるが、鋼１２，１３は冷却停止温度が高過
ぎるため、HICが発生する。又強度も低く、靭性
もよくない。
鋼１４はNiが1.12％と高く、冷却停止温度も低
過ぎるため、HIC及びSSCも発生する。
[Industrial Field of Application] The present invention provides special conditions for the composition of steel and controls hot rolling conditions and cooling conditions immediately after rolling, so that it can be used in a humid hydrogen sulfide environment (hereinafter referred to as a sour environment), especially in a high-temperature hydrogen sulfide environment. The present invention relates to a method for producing a steel sheet with excellent hydrogen-induced cracking resistance and sulfide stress corrosion cracking resistance in a humid environment containing high concentrations of hydrogen sulfide or carbon dioxide. [Prior Art] In recent years, pipelines have been laid on a large scale, but deterioration of materials due to corrosion has become a problem in such pipelines. In particular, in the pipeline transportation of oil and natural gas, crude oil and natural gas often contain hydrogen sulfide (hereinafter referred to as H 2 S) and carbon dioxide (hereinafter referred to as CO 2 ), and these H 2 S and CO 2 The problem is that atomic hydrogen, which coexists with water and is generated by corrosion, penetrates into the steel and causes destruction. Fractures that occur when atomic hydrogen generated by this corrosion penetrates into the steel include hydrogen-induced cracking (hereinafter referred to as HIC), which is a crack parallel to the sheet surface, and sulfide stress cracking, which is a crack perpendicular to the sheet surface. This is known as corrosion cracking (hereinafter referred to as SSC). The mechanism by which HIC occurs is that atomic hydrogen generated by corrosion of iron on the steel surface in a sour environment penetrates into the steel, causing the spread of layers such as MnS and oxide-based clusters in the steel. It occurs when it accumulates around inclusions. Moreover, since such layered inclusions often exist within segregation zones,
It is known that HIC that originates from inclusions is promoted by segregation zones. On the other hand, SSC is a phenomenon that occurs especially on the high strength side,
Furthermore, since welding is essential when manufacturing and laying line pipes, etc., the hardness of the welded parts of the steel used for these purposes increases, and this increases the by hydrogen of
SSC is known to occur. Conventionally, however, the following methods have been used to prevent HIC and SSC. Regarding HIC, (1) methods of suppressing corrosion of steel such as Ni, Cu, Cr, etc. or adding elements that form a stable film on the surface to reduce the amount of hydrogen that enters due to corrosion; (2) MnS with addition of Ca, REM, etc.
(3) A method of reducing the degree of segregation of the segregation zone by reducing the content of Mn, P, etc., or subjecting the rolled semi-finished product to soaking diffusion treatment, (4)
Attempts have been made to reduce HIC susceptibility mainly by improving the microstructure of segregated areas by reheating, quenching and tempering, or normalizing after rolling. On the other hand, measures to prevent SSC include (i) reducing the surface hardness of the steel plate, (ii) limiting welding conditions during construction,
Measures such as these have been taken. However, it was not possible to completely prevent HIC and SSC using an H 2 S artificial seawater saturated solution with a pH of 3.0, which has the most severe corrosive environmental conditions to date. This is because it had the following problems. The problems with HIC are as follows. [Object of the invention] Adding Cu or Ni to steel by the method (1) above.
By adding Cr, corrosion of steel is suppressed,
When attempting to suppress hydrogen intrusion into steel, there is a lower limit constraint on PH, for example, Cu
produces stable corrosion products when the pH is higher than 5, but when the pH becomes low, the corrosion products of Cu dissolve, making it impossible to suppress hydrogen intrusion. In addition, in normal pipelines, an internal cleaning device called a pig is periodically turned on to remove deposits inside the pipe. Local corrosion is unavoidable due to the scratches caused by this pig abrasion. In method (2) above, Ca, REM, etc. are added to make MnS spheroidal, which is the point where HIC occurs, but since many impurities accumulate in the center of the steel billet, MnS is not completely spherical. It is difficult to convert.
Furthermore, if the center part is to be completely spherical, large amounts of Ca and REM must be added, and cluster-like oxide-based inclusions increase outside the center part, causing HIC. Therefore, MnS, which is the origin of HIC
It is difficult to make it completely spherical. Regarding method (3), the content of elements that tend to promote segregation, such as P and Mn, is reduced as much as possible to prevent the propagation of HIC, but this method completely eliminates HIC in the following two points. Attempts to suppress it are insufficient. That is, first, even if the propagation path is removed, HIC will not disappear unless the point of occurrence is removed. Second, in view of today's industrial technology, there are limited ranges that cannot be applied to mass production, such as P in steel.
It can be pointed out that conditions must be set to extremely reduce the amount to 0.002% or less, making it impractical for practical use. The method (4) above, that is, the method of reheating after rolling and applying quenching and tempering or normalizing, is
Although the concept is basically the same as method (3), it is actually a more useful method than method (3), which cannot be adopted in mass manufacturing processes. However, as in method (3), complete HIC-free steel cannot be obtained unless the points where HIC occurs are removed. However, QT treated material has improved HIC susceptibility compared to as-rolled material with the same inclusion morphology control. On the other hand, the SSC issues are as follows. (i) The QT treatment mentioned in (4) of HIC improves the cracking susceptibility of HIC, but since it is water-cooled directly after heating, the surface hardness remains very low compared to the center of the plate thickness even after tempering. expensive. Therefore, in a sour environment, HIC
However, SSC is likely to occur, which is a problem. The limitation on the welding conditions during construction in (ii) above is because if the welding heat input is low, the heat affected zone (HAZ) will harden and a hardened structure will be generated, increasing the hardness and causing SSC. Although it increases welding heat input and reduces hardness, it has problems such as deteriorating the toughness of the HAZ part. From the above, it has not been possible to completely prevent HIC and SSC in a humid environment containing high concentrations of hydrogen sulfide or carbon dioxide. [Structure of the Invention] In order to solve the above-mentioned drawbacks, the present inventors have developed a component system,
As a result of extensive research into heating, rolling, and cooling processes, we have found that not only the strength and toughness of steel sheets but also HIC resistance and
We have now invented a completely new method for producing steel sheets with excellent SSC resistance. This point will be explained in detail below. The feature of the present invention is to extremely reduce the S content and control the morphology of MnS by adding Ca.
A steel billet containing Mo and Ti is heated, and in addition to rolling in the recrystallized region of austenite grains, a reduction of 60 to 80% is applied in the non-recrystallized region below 900°C, and rolling is completed at the Ar 3 transformation point or higher. Relatively fast cooling rate immediately after
Cooling is performed at a rate of over 20°C to 40°C/sec, water cooling is stopped at a temperature of 350°C or higher and lower than 550°C, and then left to cool. If this method is followed, the structure after cooling will be a fine bainite or a mixed structure of fine ferrite-bainite, and the hardness in the thickness direction will be constant, and the microstructure in the center segregation area will also be improved, resulting in excellent strength, toughness, and resistance. HIC SSC resistance is also greatly improved.
Furthermore, the lamellar tear resistance and weld heat affected cracking resistance are greatly improved. Therefore, the steel of the present invention is applicable to all kinds of uses (chemical plant equipment, pressure vessels, shipbuilding, line pipes, etc.). [Operations and Effects of the Invention] The reasons for limiting the heating, rolling, and cooling conditions in the present invention will be explained in detail below. First, the reason why the heating temperature is limited to 1000 to 1200°C is to keep the austenite grains small during heating and to refine the rolled structure. 1200°C is the upper limit temperature at which the austenite grains do not become coarse during heating; if the heating temperature exceeds this temperature, the austenite grains become coarse and the ferrite and bainite structures after cooling also become coarse, resulting in deterioration of the toughness of the steel. On the other hand, if the heating temperature is too low, the added alloying elements will not be sufficiently dissolved, the internal quality of the steel will deteriorate, and the temperature at the final stage of rolling will drop too much, so controlled cooling is not expected to have a sufficient effect of improving material quality. Can not. Therefore, it is necessary to set the lower limit to 1000°C. However, even if the heating temperature is limited as above, it is not possible to obtain a good material if the rolling conditions are inappropriate, so the rolling reduction in the non-recrystallization temperature range of 900°C or less is required to be at least 60%. be. This is done in order to thoroughly stretch the fine-grained austenite by adding sufficient rolling in the non-recrystallization temperature range to low-temperature heating, and to homogenize the transformed structure formed after cooling into fine grains. If it is less than %, the effect is small. In addition, the upper limit was set at 80% because if it exceeds 80%, the number of rolling passes increases and the finishing temperature cannot be ensured. Ferrite-
If the bainite structure is not made sufficiently fine, not only will the toughness deteriorate significantly, but the hardness difference in the thickness direction will increase, and SSC resistance will also deteriorate. The rolling finishing temperature is set at Ar 3 to prevent the development of a special structure, to prevent the elongation of MnS that affects HIC, and to exhibit the water cooling effect in the next process.
Above the metamorphosis point. Next is cooling after rolling, which must be carried out so as to obtain a uniform ferrite-bainite structure in the thickness direction in order to obtain good strength, toughness, HIC resistance, and SSC resistance. The cooling start temperature is preferably equal to or higher than the Ar 3 transformation point in order to obtain a uniform and fine ferrite-bainite structure. However, it is effective up to Ar 3 -30℃. However, if it is less than that, the amount of coarse ferrite in the microstructure increases and is not necessarily effective for HIC resistance. Limiting the cooling and cooling stop temperature conditions is the durability of the present invention.
This is an essential condition for improving HIC and SSC resistance, and the reason for this is described below. Cooling must be carried out immediately after the end of rolling to a temperature of 350°C or more and less than 550°C at a cooling rate in the range of more than 20°C to 40°C/sec. The reason for this is that when the temperature is less than 20°C/sec, a fine ferrite-bainite structure is difficult to form, and when it exceeds 40°C/sec, a large amount of martensite is formed, which not only deteriorates the HIC resistance but also deteriorates the toughness. Therefore, to improve HIC resistance, it is necessary to have a uniform structure and fine ferrite.
Controlling it to bainite is an essential condition. Regarding the cooling stop temperature, the lower limit was set to 350°C and the upper limit was set to less than 550°C in order to obtain uniform and fine ferrite-bainite. Figure 1 shows the water cooling stop temperature and HIC− of the steel of the present invention.
The relationship with the UST defect area rate (%) is shown. As shown in Figure 1, when the water cooling stop temperature is less than 550℃, a fine ferrite-bainite structure is formed.
The structure of the center segregation area has also been improved, and this effect has increased the resistance.
HIC characteristics are also improved. At a water-cooling stop temperature of 550° or higher, part of the pearlite structure becomes bainite, but a layered structure remains and the HIC properties are improved to some extent, but not sufficiently. Furthermore, if the temperature is below the lower limit of 350°C, a hardened structure is generated, which deteriorates the HIC properties and SSC properties. Figure 2 shows the hardness distribution in the plate thickness direction.
Steel that has been water-cooled at temperatures below ℃ has a small difference in hardness in the plate thickness direction, and has a much lower surface hardness than normal QT steel at the same strength level.As a result, the SSC resistance properties are significantly improved, making it suitable for high-strength thick-walled materials. can be manufactured. The reason for limiting the composition range of the steel of the present invention will be explained below. Among the steels of the present invention having the above characteristics, the composition range of the steel of the first invention is C: 0.12% or less, Si: 0.6% or less, Mn: 0.6
~1.5%, P: 0.015% or less, Al: 0.01~0.10%,
The basic components are Ti: 0.005 to 0.025%, Mo: 0.1 to 0.5%, and the content of S, O, and Ca is S: 0.003% or less,
O: 0.005% or less, Ca: 0.006% or less, and satisfy the following conditions: 0.7≦[Ca]/1.25[S]+0.625[O]≦1.5. The causes of HIC are (1) nonmetallic inclusions, (2) hydrogen intrusion due to corrosion reactions, and (3) internal deterioration due to segregation. First, we will discuss (1) countermeasures against nonmetallic inclusions. The impurity S in the steel of the present invention is 0.003%
Below, O is limited to 0.005% or less, Ca is limited to 0.006% or less, and the relationship between these three components is 0.7≦
The main reason for stipulating that the condition of [Ca] / 1.25 [S] + 0.625 [O] ≦ 1.5 be satisfied is the main cause of HIC occurrence.
This is due to the spheroidization of MnS and the reduction of cluster-like oxide-based inclusions, which are the starting point of HIC mainly in the low pH range. As a countermeasure to this, the amount of S in the steel, that is, the absolute amount of MnS, is reduced, and the form of MnS is controlled by adding Ca, and the amount of O, that is, the absolute amount of Al 2 O 3 is reduced, and the addition of Ca causes cluster-like formation. is an oxide
Al 2 O 3 is reduced and converted into spherical CaO.Al 2 O 3 . As a result of careful consideration of the conditions for this, the inventors determined that after reducing S to 0.003% or less,
By setting [Ca]/1.25[S]+0.625[O] to 0.7 or more, it is possible to extremely reduce elongated inclusions MnS. Similarly [Ca] / 1.25 [S] + 0.625 [O]
It is possible to minimize the amount of cluster-like oxide-based inclusions by keeping it below 1.5.
It was found that a remarkable effect on HIC resistance was observed. Therefore, the upper limit of S is set to 0.003%,
The upper limit of [Ca]/1.25 [S] + 0.625 [O] is 1.5, and the lower limit is
It was set to 0.7. Also, the lower S is, the greater the improvement effect is, 0.001%.
By doing the following, it will improve dramatically. Next, we will discuss (2) prevention of hydrogen intrusion through corrosion reactions. Atomic hydrogen generated by the corrosion reaction of Fe→Fe ++ +2e - , 2H + +2e - →2H penetrates into the steel and causes HIC. A common countermeasure is to add Cu, etc. to form a stable surface film, but this effect becomes less effective in the low pH range. Therefore, the present inventor investigated a method of preventing HIC from occurring even if hydrogen penetrates into steel in the low Hz range. (3) Regarding the deterioration of the internal quality, Mo addition to reduce center segregation and heating, rolling,
Improving the structure by limiting cooling conditions. Next, the reasons for limiting each component will be explained. The upper limit of C was set at 0.12% in order to ensure the strength of the base metal and welded part, but if it exceeds 0.12%, island-like martensite will be generated during controlled cooling, which will not only have a negative effect on ductility but also , the internal quality, weldability, and HAZ toughness are also deteriorated, so the upper limit was set at 0.12%. It should be noted that if C is less than 0.03%, the center segregation area will be greatly improved, so it is preferably less than 0.03%. Si is an element that is inevitably included in deoxidized steel, but since Si also deteriorates weldability and HAZ toughness, the upper limit was set at 0.6% (steel deoxidation can be done with Al alone, so it is preferable) is preferably 0.2% or less). Mn is an extremely important element that simultaneously improves strength and toughness. If Mn is less than 0.6%, strength cannot be ensured due to low C, and the effect of improving toughness is also small, so the lower limit was set at 0.6%. However, if too much Mn is added and the hardenability increases, a large amount of martensite tends to be generated, and center segregation becomes significant, reducing the ability to stop HIC propagation. In addition, since it deteriorates the toughness of the base material and HAZ, the upper limit was set at 1.5%. Regarding P, since it is an element that promotes center segregation, the upper limit was set to 0.015% or less. Al is an element that is inevitably contained in this type of killed steel for deoxidation, but if Al is less than 0.01%, deoxidation will be insufficient and the toughness of the base material will deteriorate, so the lower limit is set at 0.01%.
%. On the other hand, if Al exceeds 0.10%, cluster-like oxide inclusions will increase, which will have a negative impact on HIC and deteriorate HAZ toughness, so the upper limit should be
It was set to 0.10%. Ti is added in a small amount range (Ti 0.005 to 0.025%)
This is effective in forming fine TiN and refining the rolling structure and HAZ, which is effective in improving toughness. Also Ti,
MnS, which causes HIC due to the synergistic effect of Ca
It also has the effect of making it spherical. Therefore, the lower limit of the amount of Ti added is the minimum amount that exhibits the effect on the material, and the upper limit is the minimum amount that can be obtained under the conditions that fine TiN can be obtained in the steel billet by normal manufacturing methods and that toughness does not deteriorate due to TiC. It was set as 0.025%. Mo is an effective element for HIC in low pH environments, but this effect is small below 0.1%.
Moreover, if it is 0.5 or more, this effect will be weak and the cost will increase, so the upper limit was set at 0.5%. I have already explained in detail about O and Ca,
The upper limit of O was set at 0.005% because if it exceeds 0.005%, cluster-like oxide inclusions will increase and cause HIC. Regarding Ca, there is a relationship with ICP, but the upper limit of Ca amount is
The reason why it is limited to 0.006% is the same as for O. If it exceeds 0.006%, cluster-like oxide inclusions increase.
The upper limit was set at 0.006% because it causes HIC. In the second invention set forth in claim 2, in addition to the composition and manufacturing process of the steel of the first invention set forth in claim 1, Nb: 0.10% or less, V:
0.10% or less, Ni: 1.0% or less, Cu: 1.0% or less,
Cr: 1.25% or less, B: 0.005% or less, type 1 or 2
It contains more than one species. The main purpose of adding these elements is to improve the strength and toughness of the steel of the present invention and to increase the thickness of the manufactured plate without impairing the characteristics of the steel, and the amount of these elements should be limited by themselves. It is. Nb is included to refine the rolling structure, improve hardenability, and precipitation harden, and is an important element that improves both strength and toughness.
Adding more than 0.10% has no effect on the material and is harmful to weldability and HAZ toughness, so the upper limit should be set.
Limited to 0.10%. V has almost the same effect as Nb, but an upper limit of 0.10% is permissible for both. Ni is an effective element for corrosion resistance, HIC resistance, etc., and also improves the strength and toughness of the base metal. However, if it exceeds 1%, it is unfavorable for SSC resistance, HAZ hardenability, and toughness, so the upper limit was set at 1%. As mentioned above, Cu is effective in preventing hydrogen intrusion in a sour environment with relatively high pH, but if it exceeds 1%, Cu cracks will occur during rolling even if Ni is added, making manufacturing difficult. For this reason, the upper limit was set at 0.1%. Cr increases the strength of the base metal and the welded part, and is effective in HIC resistance, etc., but if too much is lost, it increases the hardenability of the HAZ, resulting in a decrease in toughness and weldability, which is undesirable. The upper limit is 1.25%. B segregates at austenite grain boundaries during rolling and improves hardenability and facilitates the formation of bainite structure, but when it exceeds 0.005%, BN and B constituents are formed, which deteriorates the toughness of the base metal and HAZ. let For this reason, the upper limit was set at 0.005%. [Example] Next, an example of the present invention will be described. Steel plates with a thickness of 12 to 32 mm were manufactured using slabs having the chemical composition shown in Table 1, which were manufactured in a continuous converter casting process, by changing the heating, rolling, and cooling processes. Steels 1 to 9 are inventive steels, and steels 10 to 14 are comparison steels. Table 2 shows mechanical properties, HIC resistance, SSC resistance
Show characteristics. The HIC test uses a test piece with a thickness of 1 mm cut from the front and back sides of a steel plate, a width of 20 mm, and a length of 100 mm.
The SSC test was conducted using a test piece with a thickness of 3 mm, width of 10 mm, and length of 115 mm. As for the test conditions, the HIC test was conducted without applying external stress, and the SSC test was performed using a four-point bending jig to apply a deflection equivalent to the yield stress to the test piece. The immersion conditions are 25℃ H2S saturation and 0.5% CH3COOH .
The HIC test piece was immersed in -5% NaCl aqueous solution (PH3) for 4 days, and the SSC test piece was immersed for 21 days. The immersion results are shown in Table 2. Among the comparative steels, Steel 10 has a low ICP of 0.30, so HIC occurs even though the other conditions are within the range of appropriate manufacturing conditions. Steel 11 is the opposite of steel 10 because its ICP is high at 1.66.
HIC occurs. Steels 10 and 11 have the same chemical composition as Invention Steels 3 to 5, but HIC occurs in Steels 12 and 13 because the cooling stop temperature is too high. It also has low strength and poor toughness. Steel 14 has a high Ni content of 1.12% and the cooling stop temperature is too low, so HIC and SSC also occur.
【表】【table】
【表】【table】
【表】【table】
第１図は水冷停止温度と耐HIC特性、機械的性
質（TS、Ｂ・DWIT）の関係を示すグラフ、第
２図は鋼４と通常QT材の板厚方向の硬度分布を
示す図である。
Figure 1 is a graph showing the relationship between water cooling stop temperature, HIC resistance, and mechanical properties (TS, B・DWIT), and Figure 2 is a graph showing the hardness distribution in the thickness direction of Steel 4 and regular QT material. .
Claims (1)
1.5％、Ｐ：0.015％以下、Al：0.01〜0.10％、
Ti：0.005〜0.025％、Mo：0.1〜0.5％を基本成分
としてＳ、Ｏ、Caの含有量がＳ：0.003％以下、
Ｏ：0.005％以下、Ca：0.006％以下であつて、か
つ次式(1)、(2) 0.7≦ICP≦1.5 ………(1) ICP＝〔Ca〕／1.25〔Ｓ〕＋0.625〔Ｏ〕 ………(2) を満足する成分を含有し、残部がFe及び不可避
的不純物からなる鋼片を、1000〜1200℃に加熱
し、その後の圧延に当つて900℃以下の圧下量60
〜80％、仕上り温度Ar3変態点以上で圧延を行な
い、圧延終了後、冷却速度20超〜40℃／secで350
℃以上550℃未満の温度まで冷却し、その後放冷
することを特徴とする耐水素誘起割れ性及び耐硫
化物応力腐食割れ性の優れた鋼板の製造方法。 ２ Ｃ：0.12％以下、Si：0.6％以下、Mn：0.6〜
1.5％、Ｐ：0.015％以下、Al：0.01〜0.10％、
Ti：0.005〜0.025％、Mo：0.1〜0.5％を基本成分
とし、さらにNi：1.0％以下、Cu：1.0％以下、
Cr：1.25％以下、Nb：0.10％以下、Ｖ：0.10％以
下、Ｂ：0.005％以下の一種または二種以上を含
有し、Ｓ、Ｏ、Caの含有量がＳ：0.003％以下、
Ｏ：0.005％以下、Ca：0.006％以下であつて、か
つ次式(1)、(2) 0.7≦ICP≦1.5 ………(1) ICP＝〔Ca〕／1.25〔Ｓ〕＋0.625〔Ｏ〕 ………(2) を満足する成分を含有し、残部がFe及び不可避
的不純物からなる鋼片を、1000〜1200℃に加熱
し、その後の圧延に当つて900℃以下の圧下量60
％〜80％、仕上温度Ar3変態点以上で圧延を行な
い、圧延終了後、冷却速度20超〜40℃／secで350
℃以上550℃未満の温度まで冷却し、その後放冷
することを特徴とする耐水素誘起割れ性及び耐硫
化物応力腐食割れ性の優れた鋼板の製造方法。[Claims] 1 C: 0.12% or less, Si: 0.6% or less, Mn: 0.6~
1.5%, P: 0.015% or less, Al: 0.01-0.10%,
The basic components are Ti: 0.005 to 0.025%, Mo: 0.1 to 0.5%, and the content of S, O, and Ca is S: 0.003% or less,
O: 0.005% or less, Ca: 0.006% or less, and the following formulas (1), (2) 0.7≦ICP≦1.5……(1) ICP=[Ca]/1.25[S]+0.625[ O] ......A steel billet containing components that satisfy (2), with the remainder consisting of Fe and unavoidable impurities, is heated to 1000 to 1200°C, and then rolled with a reduction amount of 60°C or less of 900°C.
Rolling is carried out at ~80%, finish temperature Ar 3 transformation point or above, and after rolling is completed, the cooling rate is over 20 ~ 40℃/sec to 350℃.
1. A method for producing a steel plate with excellent hydrogen-induced cracking resistance and sulfide stress corrosion cracking resistance, which comprises cooling to a temperature of ℃ or higher and lower than 550℃, and then allowing it to cool. 2 C: 0.12% or less, Si: 0.6% or less, Mn: 0.6~
1.5%, P: 0.015% or less, Al: 0.01-0.10%,
The basic components are Ti: 0.005 to 0.025%, Mo: 0.1 to 0.5%, and further Ni: 1.0% or less, Cu: 1.0% or less,
Contains one or more of Cr: 1.25% or less, Nb: 0.10% or less, V: 0.10% or less, B: 0.005% or less, and the content of S, O, and Ca is S: 0.003% or less,
O: 0.005% or less, Ca: 0.006% or less, and the following formulas (1), (2) 0.7≦ICP≦1.5……(1) ICP=[Ca]/1.25[S]+0.625[ O] ......A steel billet containing components that satisfy (2), with the remainder consisting of Fe and unavoidable impurities, is heated to 1000 to 1200°C, and then rolled with a reduction amount of 60°C or less of 900°C.
% to 80%, rolling is carried out at a finishing temperature of Ar 3 or above the transformation point, and after rolling is completed, the cooling rate is over 20 to 40℃/sec to 350
1. A method for producing a steel plate with excellent hydrogen-induced cracking resistance and sulfide stress corrosion cracking resistance, which comprises cooling to a temperature of ℃ or higher and lower than 550℃, and then allowing it to cool.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13872483A JPS6033310A (en) | 1983-07-30 | 1983-07-30 | Manufacture of steel plate efficient in hydrogen induced crack resistance and sulfide stress corrosion crack resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13872483A JPS6033310A (en) | 1983-07-30 | 1983-07-30 | Manufacture of steel plate efficient in hydrogen induced crack resistance and sulfide stress corrosion crack resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6033310A JPS6033310A (en) | 1985-02-20 |
| JPS631369B2 true JPS631369B2 (en) | 1988-01-12 |
Family
ID=15228664
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13872483A Granted JPS6033310A (en) | 1983-07-30 | 1983-07-30 | Manufacture of steel plate efficient in hydrogen induced crack resistance and sulfide stress corrosion crack resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6033310A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6384184A (en) * | 1986-09-29 | 1988-04-14 | Matsushita Electric Ind Co Ltd | Semiconductor laser device |
| WO2019058420A1 (en) | 2017-09-19 | 2019-03-28 | 新日鐵住金株式会社 | Steel pipe and steel plate |
| WO2020003499A1 (en) | 2018-06-29 | 2020-01-02 | 日本製鉄株式会社 | Steel pipe and steel sheet |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61221326A (en) * | 1985-03-27 | 1986-10-01 | Nippon Kokan Kk <Nkk> | Production of steel material having excellent resistance to sulfide corrosion cracking |
| JPH064902B2 (en) * | 1985-05-07 | 1994-01-19 | 新日本製鐵株式会社 | Steel material for anti-sour, which has excellent resistance to stress corrosion cracking in welds |
| JPS62112722A (en) * | 1985-11-13 | 1987-05-23 | Nippon Steel Corp | Production of steel sheet having excellent resistance to hydrogen induced cracking and resistance to sulfide stress corrosion cracking |
| JPS62290847A (en) * | 1986-06-11 | 1987-12-17 | Nippon Kokan Kk <Nkk> | Steel having superior resistance to sulfide stress corrosion cracking and its manufacture |
| JPH0730393B2 (en) * | 1988-12-25 | 1995-04-05 | 株式会社神戸製鋼所 | Method for producing steel sheet having excellent resistance to hydrogen-induced cracking |
| JPH07176U (en) * | 1991-06-06 | 1995-01-06 | 悦雄 谷原 | Foldable clothes rack |
| JP5098256B2 (en) * | 2006-08-30 | 2012-12-12 | Ｊｆｅスチール株式会社 | Steel sheet for high-strength line pipe with low yield stress reduction due to the Bauschinger effect with excellent hydrogen-induced cracking resistance and method for producing the same |
| JP6032166B2 (en) * | 2013-09-20 | 2016-11-24 | Ｊｆｅスチール株式会社 | Method for estimating hydrogen-resistant cracking characteristics of calcium-added steel |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5538901A (en) * | 1978-03-17 | 1980-03-18 | Nippon Kokan Kk <Nkk> | Manufacture of unrefined steel sheet having excellent hydrogen cracking resistance in wet hydrogen sulfide environment of high hydrogen ion concentration |
| JPS5785928A (en) * | 1980-11-14 | 1982-05-28 | Nippon Kokan Kk <Nkk> | Manufactue of nonrefined high tensile steel with superior sulfide corrosion cracking resistance |
-
1983
- 1983-07-30 JP JP13872483A patent/JPS6033310A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5538901A (en) * | 1978-03-17 | 1980-03-18 | Nippon Kokan Kk <Nkk> | Manufacture of unrefined steel sheet having excellent hydrogen cracking resistance in wet hydrogen sulfide environment of high hydrogen ion concentration |
| JPS5785928A (en) * | 1980-11-14 | 1982-05-28 | Nippon Kokan Kk <Nkk> | Manufactue of nonrefined high tensile steel with superior sulfide corrosion cracking resistance |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6384184A (en) * | 1986-09-29 | 1988-04-14 | Matsushita Electric Ind Co Ltd | Semiconductor laser device |
| WO2019058420A1 (en) | 2017-09-19 | 2019-03-28 | 新日鐵住金株式会社 | Steel pipe and steel plate |
| WO2020003499A1 (en) | 2018-06-29 | 2020-01-02 | 日本製鉄株式会社 | Steel pipe and steel sheet |
| KR20210021068A (en) | 2018-06-29 | 2021-02-24 | 닛폰세이테츠 가부시키가이샤 | Steel pipe and steel plate |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6033310A (en) | 1985-02-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4951997B2 (en) | A method for producing a high-tensile steel sheet having a tensile strength of 550 MPa or more. | |
| JPH11140580A (en) | Continuously cast slab for high strength steel excellent in toughness at low temperature, its production, and high strength steel excellent in toughness at low temperature | |
| KR20200066512A (en) | Ultra high strength steel material having excellent cold workability and sulfide stress cracking resistance and method of manufacturing the same | |
| JPS62112722A (en) | Production of steel sheet having excellent resistance to hydrogen induced cracking and resistance to sulfide stress corrosion cracking | |
| JPS631369B2 (en) | ||
| JP3941211B2 (en) | Manufacturing method of steel plate for high-strength line pipe with excellent HIC resistance | |
| JP3502691B2 (en) | Fitting material excellent in hydrogen-induced cracking resistance and sulfide stress corrosion cracking resistance and method for producing the same | |
| JP2000256777A (en) | High tensile strength steel plate excellent in strength and low temperature toughness | |
| JPS61165207A (en) | Manufacture of unrefined steel plate excellent in sour-resistant property | |
| US6258181B1 (en) | Structural steel excellent in wear resistance and fatigue resistance property and method of producing the same | |
| JPS59232225A (en) | Manufacture of bent pipe with high tension and toughness | |
| JP5008879B2 (en) | High strength steel plate with excellent strength and low temperature toughness and method for producing high strength steel plate | |
| JPH1180833A (en) | Production of steel sheet for high strength line pipe excellent in hic resistance | |
| JPH03211230A (en) | Production of low alloy steel for line pipe with high corrosion resistance | |
| JPH0225968B2 (en) | ||
| JP3526723B2 (en) | Ultra high strength steel pipe with excellent low temperature crack resistance | |
| JP2002339037A (en) | High tensile strength steel having excellent low temperature joint toughness and ssc resistance, and production method therefor | |
| JPH09324216A (en) | Manufacture of high strength steel or line pipe, excellent in hic resistance | |
| JPH06293914A (en) | Production of low alloy steel plate for line pipe excellent in co2 corrosion resistance and haz toughness | |
| JPH09324217A (en) | Manufacture of high strength steel for line pipe, excellent in hic resistance | |
| JPH0319285B2 (en) | ||
| KR100345704B1 (en) | A method of manufacturing high strength hot rolled steel strip with low susceptibility of SSCC | |
| JPH0813087A (en) | Steel for welded steel pipe excellent in ssc resistance in seam zone | |
| JPH08295929A (en) | Production of sour resistant steel sheet for line pipe excellent in co2 corrosion resistance and low temperature toughness | |
| JPS637328A (en) | Production of steel having excellent sulfide corrosion cracking resistance |